U.S. patent number 4,318,779 [Application Number 06/148,943] was granted by the patent office on 1982-03-09 for method of manufacture of blast furnace cokes containing substantial amounts of low grade coals.
This patent grant is currently assigned to Sumikin Coke Company Ltd., Sumitomo Metal Industries Limited. Invention is credited to Keiji Kubo, Hiromichi Takahashi, Michio Tsuyuguchi.
United States Patent |
4,318,779 |
Tsuyuguchi , et al. |
March 9, 1982 |
Method of manufacture of blast furnace cokes containing substantial
amounts of low grade coals
Abstract
Blast furnace coke containing low grade coal in a high blending
ratio is manufactured by a method which comprises blending not less
than 60% of a blended coal having an adjusted total moisture
content of not more than 4% with not more than 40% of briquettes
and carbonizing the resultant mixture. The blended coal consists
essentially of not less than 80% of coking coal and not more than
20% of low grade coal. When coking coal of a kind which has its
coking property segregated according to its grain size distribution
is pulverized and classified by sifting and the portion of fine
particles is used as mixed with the coking coal, the blending ratio
of the low grade coal in the blended coal can be increased to up to
35%. The briquettes consist essentially of not less than 10% of
coking coal and not more than 90% of low grade coal.
Inventors: |
Tsuyuguchi; Michio (Wakayama,
JP), Kubo; Keiji (Wakayama, JP), Takahashi;
Hiromichi (Wakayama, JP) |
Assignee: |
Sumikin Coke Company Ltd.
(Wakayama, JP)
Sumitomo Metal Industries Limited (Osaka,
JP)
|
Family
ID: |
26374477 |
Appl.
No.: |
06/148,943 |
Filed: |
May 12, 1980 |
Foreign Application Priority Data
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May 14, 1979 [JP] |
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54-59258 |
Mar 19, 1980 [JP] |
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55-35479 |
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Current U.S.
Class: |
201/6; 201/21;
201/23; 201/24; 201/8 |
Current CPC
Class: |
C10B
57/04 (20130101) |
Current International
Class: |
C10B
57/04 (20060101); C10B 57/00 (20060101); C10B
053/00 (); C10B 053/08 (); C10B 055/02 (); C10B
057/04 () |
Field of
Search: |
;201/6,8,23,24,21,40 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
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2643635 |
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Jan 1978 |
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DE |
|
2752479 |
|
May 1979 |
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DE |
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46/7375 |
|
Feb 1971 |
|
JP |
|
50/10301 |
|
Feb 1975 |
|
JP |
|
680451 |
|
Nov 1949 |
|
GB |
|
Primary Examiner: Garris; Bradley
Attorney, Agent or Firm: Watson, Cole, Grindle &
Watson
Claims
We claim:
1. A method of preparing an effective blast furnace coke which
contains substantial amounts of low grade coal, said method
comprising the steps of
(a) mixing together an amount of coking coal and an amount of low
grade coal to form a first blended coal mixture; said amount of
coking coal comprising not less than 80% by weight of the weight of
the first blended coal mixture and said amount of low grade coal
comprising not more than 20% by weight of the weight of the first
blended coal mixture,
(b) adjusting the moisture content of the first blended coal
mixture obtained in step (a) to 4% or less,
(c) mixing together an amount of coking coal, an amount of low
grade coal and an amount of an additive material selected from the
group consisting of binding substances and caking substances to
form a second blended coal mixture; said amount of coking coal
comprising not less than 10% by weight of the weight of the second
blended coal mixture and said amount of low grade coal comprising
not more than 90% by weight of the weight of the second blended
coal mixture,
(d) forming uniformly shaped briquettes from the second blended
coal mixture obtained in step (c),
(e) mixing an amount of the briquettes formed in step (d) with an
amount of the moisture content-adjusted first blended coal mixture
formed in step (b) to form a third blended coal mixture; said
amount of briquettes comprising not more than 40% by weight of the
weight of the third blended coal mixture and said amount of
moisture content-adjusted first blended coal mixture comprising not
less than 60% by weight of the weight of the third blended coal
mixture, and
(f) carbonizing the third blended coal mixture to form the blast
furnace coke.
2. The method as set forth in claim 1 wherein prior to use in step
(e) the briquettes formed in step (d) are adjusted in moisture
content to 4% or less.
3. The method as set forth in claim 1 wherein the initial moisture
contents of the coking coal and the low grade coal which are mixed
together in step (c) to form the second blended coal mixture are
adjusted prior to being mixed together such that the briquettes
formed from the second blended coal mixture in step (d) have a
moisture content of 4% or less.
4. A method of preparing an effective blast furnace coke which
contains substantial amounts of low grade coal, said method
comprising the steps of
(a) pulverizing a coking coal whose coking properties are
segregated according to its grain size distribution,
(b) depositing the pulverized coking coal of step (a) on a screen
and recovering the fine particles of pulverized coking coal which
pass through the screen,
(c) mixing the recovered fine particles of pulverized coking coal
obtained in step (b) with another coking coal to form a coking coal
mixture,
(d) mixing together an amount of the coking coal mixture obtained
in step (c) with an amount of low grade coal to form a first
blended coal mixture, said amount of coking coal mixture comprising
not less than 65% by weight of the weight of the first blended coal
mixture and said amount of low grade coal comprising not more than
35% by weight of the weight of the first blended coal mixture,
(e) adjusting the moisture content of the first blended coal
mixture obtained in step (d) to 4% or less,
(f) mixing together an amount of coking coal, an amount of low
grade coal and an amount of an additive material selected from the
group consisting of binding substances and caking substances to
form a second blended coal mixture; said amount of coking coal
comprising not less than 10% by weight of the weight of the second
blended coal mixture and said amount of low grade coal comprising
not more than 90% by weight of the weight of the second blended
coal mixture,
(g) forming uniformly shaped briquettes from the second blended
coal mixture obtained in step (f),
(h) mixing an amount of the briquettes formed in step (g) with an
amount of the moisture content-adjusted first blended coal mixture
obtained in step (e) to form a third blended coal mixture; said
amount of briquettes comprising not more than 40% by weight of the
weight of the third blended coal mixture and said amount of
moisture content-adjusted first blended coal mixture comprising not
less than 60% by weight of the weight of the third blended coal
mixture, and
(i) carbonizing the third blended coal mixture to form the blast
furnace coke.
5. The method as set forth in claim 4 wherein prior to use in step
(h) the briquettes formed in step (g) are adjusted in moisture
content to 4% or less.
6. The method as set forth in claim 4 wherein the initial contents
of the coking coal and the low grade coal which are mixed together
in step (f) to form the second blended coal mixture are adjusted
prior to being mixed together such that the briquettes formed from
the second coal mixture in step (g) have a moisture content of 4%
or less.
7. The method as set forth in claim 4 wherein said another coking
coal in step (c) comprises the particles of pulverized coking coal
retained by the screen in step (b) which have been further
pulverized.
8. The method as set forth in claim 4 wherein the coking coal used
in step (f) comprises the particles of pulverized coking coal
retained by the screen in step (b) which have been further
pulverized.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention:
The present invention is directed to a method of manufacturing an
effective blast furnace coke, and more particularly to a method of
manufacturing an effective blast furnace coke which contains a
substantial amount of low grade coal.
2. Description of the Prior Art:
It is well known that blast furnaces, and especially large sized
blast furnaces, require high quality cokes to sustain their
operation. At the same time, however, due to the current global
shortage of good quality coals, the price of effective blast
furnace cokes has gone up. In order to compensate, the coke
industry has developed a number of manufacturing processes for the
production of blast furnace cokes which can utilize low grade
coals, e.g., non-coking coals or poorly coking coals (these being
the coals which account for most of the available coals and are the
cheapest in cost, but which heretofore have not been considered
suitable for use as raw material coals for the manufacture of blast
furnace cokes). However, none of these processes have been found to
be totally acceptable.
For example, the following manufacturing processes have been
developed which make use of low grade coals: a preheated coal
charging process (coaltek system or precarbon system) wherein some
or all of either a coking coal or a blended coal, which consists of
a coking coal and a low grade coal, is preheated at temperatures of
from 200.degree. C. to 350.degree. C. and then charged into the
coke oven (see Japanese Patent Publication No. 23495/46, published
on July 5, 1971); a partial briquette charging process wherein
briquettes containing low grade coal are added to a blended coal to
be charged into the coke oven (see Japanese Patent Publication No.
7375/46, published on Feb. 24, 1971); a caking substance adding
process wherein a charging coal is prepared by adding artifical
coking coal or a caking substance to blended coal (see JA-OS
85803/53, laid open for public inspection on July 28, 1978); and a
selective pulverization process wherein a coking coal of a kind
which has its coking property segregated according to its grain
size distribution is pulverized by use of a sieve (see Japanese
Patent Publication No. 45763/49, published on Dec. 6, 1974 and
Japanese Patent Publication No. 19321/53, published on June 20,
1978).
The above noted preheated coal charging process is believed to
provide enhanced strength to the produced coke because the bulk
density of the coal charged into the coke oven is increased and the
spaces between adjacent coal particles are decreased, and also
because the 100.degree. C. zone is totally absent or short during
the vaporization of the moisture, the heating rate in the plastic
zone is lowered, the thickness of the plastic layer is expanded,
and the possibility of adjacent coal particles coalescing is
enhanced. Although the blending ratio of the low grade coal is
variable with the particular kind of coal being used, it is thought
to have a limit of 20% by weight (hereinafter indicated simply in
%).
In the case of the above-noted partial briquette charging process,
various views have been advanced as to the mechanism which leads to
the manifestation of its effect. A typical theory is that expansion
of the briquettes in the coking process causes compaction of the
coal surrounding the briquettes, which results in an improvement in
the coking property. When the blending ratio of briquettes is 60%,
incidentally, the bulk density of the coal charged in the coke oven
reaches its peak and the stength of the produced coke is improved
to the greatest extent. In the operation of this system on a
commercial scale, however, the segregation which occurs in the
briquettes in the coke oven results in difficulties in discharging
the produced coke from the coke oven. Thus, the blending ratio of
briquettes is said to be generally limited to about 30%. The
proportion of low grade coal which can be blended in total amount
of the charging coal is about 20%, though it is variable with the
type of low grade coal which is used.
The above-noted caking substance adding process aims to overcome
the fluidity problems and improve the quality of the produced coke
by the addition of a caking substance. The quality of the caking
substance, therefore, is important. Since the caking substance is
generally higher in cost than the coal, the proportion of the
caking substance economically desirable for addition to the
charging coal is generally limited to about 10%. For this reason,
the blending ratio of low grade coal is said to be about 20%.
The above-noted selective pulverization process aims to improve the
coking property of the charging coal by pulverizing coking coal of
a kind which has its coking property segregated according to its
grain size distribution, screening the pulverized particles through
a sieve 3 to 6 mm in mesh size and pulverizing again the course
particles retained on the sieve, whereby the inert particles which
reduce the coking property and are concentrically present in the
coarse-particle zone will be uniformly distributed throughout the
charging coal.
With any of the processes described above, however, the highest
possible blending ratio for the low grade coal in the charging coal
is about 20%. Thus, the need of developing a method capable of
producing a blast furnace coke containing low grade coal in an
increased blending ratio has become pressing. Research and
developments, thereto, are being promoted on this subject from
various angles.
It is, therefore, an object of this invention to provide a method
for the manufacture of blast furnace coke by blending low grade
coal with coking coal in a high blending ratio.
Another object of the present invention is to provide a method for
the manufacture of blast furnace coke by the operation of the
partial briquette charging system without necessitating any special
means for the prevention of segregation.
SUMMARY OF THE INVENTION
According to the present invention, which combines the partial
briquette charging system with the requirement that the total
moisture content of the blended coal be lowered to at or below 4%,
as the segregation of briquettes in the coke oven is decreased, the
blending ratio of briquettes can be increased to 40% in an actual
commercial operation without necessitating any special means for
preventing the segregation. In addition, the effect of the addition
of the caking substance in the briquettes can be promoted and the
blending ratio of low grade coal can be notably increased, i.e., by
keeping the total moisture content in the briquettes at 4% or
below.
Further, this invention allows the blending ratio of the low grade
coal to be increased to a still higher level by a procedure which
comprises pulverizing coking coal of a kind which has its coking
property segregated according to its grain size distribution (such
as Australia and Canada origin), mixing the fine particles which
have passed the sieve with the other coking coal, blending not less
than 65% of the resultant mixture with not more than 35% of low
grade coal to produce a blended coal, treating the blended coal so
as to keep the total moisture content thereof at or below 4%,
separately preparing briquettes comprising not less than 10% of
coking coal, not more than 90% of low grade coal and a binder
and/or caking substance, blending not less than 60% of the
aforementioned blended coal with not more than 40% of the
briquettes and thereafter carbonizing the resultant blend. The
effect of this invention is additionally improved when the
briquettes have their total moisture content adjusted to a level of
not more than 4% and when the coarse particles retained on the
sieve after pulverizing of coking coal of a kind which has its
coking property segregated according to its grain size distribution
are again pulverized and used as a substitute for the coking coal
in the blended coal or the coking coal in the briquettes.
Other objects, characteristics and advantages of this invention
will become apparent from the further disclosure of invention found
herein below and considered in conjunction with the accompanying
drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic diagram of the test apparatus used in Example
2 of the specification and
FIG. 2 is a graph showing the relationship between the total
moisture content of the briquettes and the coke strength as
discussed in Example 3.
DETAILED DESCRIPTION OF THE INVENTIVE EMBODIMENTS
In the following description of this invention, the terms indicated
below will be used as defined correspondingly.
By "coking coal" is meant strongly coking coal to weakly coking
coal.
By "low grade coal" is meant non-coking coal or poorly coking coal
which has the properties of CSN (FSl) 0-2, flowability index 0-10
D.D.P.M., and total dilation index (Audibert Arnu dilatometer) of
0, and which has heretofore been refused acceptance, i.e., has been
considered unsuitable, for use in the manufacture of blast furnace
coke.
By "blending coal" is meant a coal which includes coking coals or a
mixture consisting of desired proportions of coking coal and low
grade coal and has been adjusted to have a CSN in the range of 3 to
9 and volatile matter in the range of 25 to 33%.
By "charging coal" is meant a coal which has been prepared by
solely using blended coal or by mixing blended coal with briquettes
or a caking substance and is ready to be charged into a coke
oven.
By "briquette" is meant a product obtained by blending coking coal
and low grade coal in a desired blending ratio, adding a caking
substance and/or binder to the resultant blend, kneading the
mixture and molding it in a unform shape under a roll press.
By "caking substance" is meant an aromatic bituminous substance.
For example, coal pitch, asphalt pitch and those pitches which are
obtained by heat-treatment or solvent-extraction of coal tar,
asphalt, bottom oil remaining after removal of the 230.degree. C.
fraction from coal tar (hereinafter referred to as "road tar"),
coal pitch, petroleum heavy oil, etc., can be utilized as the
caking substance. They may be used in conjunction with solvents
such as coal tar, road tar, propane-deasphalting asphalt (PDA),
etc. They are invariably capable of improving the coking property
and are generally added in a blending ratio of 1 to 30%.
The binder is used for the purpose of enabling the briquettes to
retain their original shape. Coal pitch, asphalt, road tar, coal
tar, etc., can be used as binders and are generally added in a
blending ratio of 5 to 15%.
The first embodiment of this invention comprises causing a blended
coal, prepared by mixing not less than 80% of coking coal with not
more than 20% of low grade coal, to be preheated or dried to adjust
the total moisture content thereof to at or below 4%, separately
preparing briquettes by combining not less than 10% of coking coal,
not more than 90% of low grade coal and a binder and/or caking
substance, then mixing not more than 40% of the briquettes with not
less than 60% of the blended coal having an adjusted total moisture
content of not more than 4%, and thereafter carbonizing the
resultant blend.
In the first embodiment of this invention, the segregation of
briquettes occurs less than in the ordinary blended coal (having a
total moisture content of 8%), the blending ratio of briquettes can
be increased to up to 40%, even when the manufacture is practiced
on a commercial scale, and the blending ratio of low grade coal can
be substantially increased because the blended coal is adjusted
such that its total moisture content is lowered to 4% or below.
When the total moisture content of the briquettes is additionally
lowered to at or below 4%, the thickness of the plastic layer in
the plastic zone is increased similarly to the charging coal
involved in the preheated coal charging process, the effect of the
addition of caking substance is promoted and the blending ratio of
the low grade coal can be increased. Consequently, nearly one half
the entire amount of the charging coal can comprise low grade
coal.
The upper limit to the blending ratio of low grade coal in the
blended coal destined to have its total moisture content lowered to
or below 4% is fixed at 20%. The reason for this upper limit of 20%
is that the coke strength of the blended coal becomes insufficient
(note: under special conditions the blending ratio of low grade
coal can exceed 20%).
The upper limit to the blending ratio of low grade coal in the coal
material of the briquettes is fixed at 90%. The reason for this
limit is that the coke strength becomes insufficient when the
blending ratio of low grade coal exceeds 90%.
The upper limit to the total moisture content of the blended coal
is fixed at 4%. The reason for this limit is that the coke strength
of the blended coal becomes insufficient, the segregation of the
briquettes increases, and the blending ratio of briquettes is
consequently lowered when the moisture content exceeds 4%.
The blending ratio of briquettes can be increased by adjusting the
total moisture content of the blended coal as described above. As
already described, the blending ratio of low grade coal is further
increased when the total moisture content of the briquettes is
additionally lowered to at or below 4%.
The preparation of briquettes having a total moisture content of
not more than 4% may be practiced by first kneading the coal
material having its total moisture content suitably adjusted in
advance and then forming the coal material into briquettes under a
roll press, or by first forming the coal material into briquettes
under a roll press and then treating the briquettes to have their
total moisture content adjusted. The effect of the adjustment of
total moisture content is the same regardless of which of the two
methods described above is used.
The second embodiment of this invention comprises pulverizing
coking coal of a kind which has its coking property segregated
according to its grain size distribution, screening the pulverized
coal through a sieve, pulverizing further the coarse particles
retained on the sieve, then mixing the fine particles collected
under the sieve, another coking coal and low grade coal to produce
a blended coal and thereafter adjusting the total moisture content
of the resultant blend. It may alternatively comprise pulverizing
coking coal of a kind which has its coking property segregated
according to its grain size distribution, screening the pulverized
coal through a sieve, further pulverizing the coarse particles
retained on the sieve and using the pulverized particles as a
substitute for the coking coal in the briquettes.
Specifically, according to the second embodiment of this invention,
in the manufacture of blast furnace coke by the carbonization of
the charging coal prepared by blending the blended coal with the
briquettes, the coking coal of a kind which has its coking property
segregated according to its grain size distribution is first
pulverized and the pulverized coal is screened through a sieve, the
fine particles collected under the sieve are mixed with another
coking coal, not less than 65% of the resultant mixture and not
more than 35% of low grade coal are combined to form a blended
coal, and the blended coal is treated to have its total moisture
content lowered to at or below 4%. Separately, briquettes are
prepared with not less than 10% of coking coal, not more than 90%
of low grade coal and a binder and/or a caking substance.
Thereafter, not less than 60% of the aforementioned blended coal
and not more than 40% of the briquettes are blended and subjected
to carbonization.
The preheated coal charging process has the effect of increasing
the bulk density of the charging coal in the coke oven, promoting
the compaction of the coal particles, and assisting in the action
of mutual fusion between the low molecular weight portion and the
higher molecular weight portion in the plastic zone. When this
process is used in combination with the aforementioned selective
pulverization system, a synergistic effect is achieved in that the
dispersion of the low molecular weight portion is promoted in the
course of preheating because the inert particles which are
inhibitory of the coking property and concentrically present in the
course particles portion are allowed to be uniformly distributed
throughout the blended coal. As a result, the blending ratio of low
grade coal can be notably increased. Moreover, since the total
moisture content of the blended coal is adjusted to, similarly to
that in the first embodiment, at or below 4%, preparatorily to the
mixing of the blended coal with the briquettes, the segregation of
briquettes in the coke oven is decreased, the blending ratio of the
briquettes during the commercial operation of the invention can be
increased up to 40% without necessitating any special means for
precluding the segregation, and the blending ratio of low grade
coal can be increased.
Also in the second embodiment, when the total moisture content of
the briquettes is additonally adjusted to at or below 4%, the
addition which is made as one of the effects of the preheating to
the thickness of the plastic layer in the plastic zone furthers the
possibility of adjacent coal particles being united and permits the
blending ratio of the low grade coal in the briquettes to be
proportionately increased. The effect just described when
additionally adding the caking substance during the preparation of
briquettes is advanced and the blending ratio of low grade coal in
the briquettes is further increased. When the coarse particles
retained on the sieve are pulverized again and are added into the
briquettes, the amount of the fine particles collecting under the
sieve is changed and the blending ratio of low grade coal in the
blended coal is increased.
For the reasons described in detail above, the present invention,
which uses a specific combination of steps, permits manufacture of
blast furnace coke from a charging coal containing up to 50% of low
grade coals.
In the second embodiment, the upper limit to the blending ratio of
low grade coal in the blended coal is fixed at 35%. The reason for
this upper limit is that the coke strength becomes insufficient
when the blending ratio of low grade coal exceeds 35%.
The reasons for and the effects of fixing the upper limit to the
blending ratio of low grade coal in the briquettes at 90%,
adjusting the total moisture content of the blended coal at or
below 4% and fixing the upper limit to the total moisture content
of the briquettes at 4% are the same as those of the first
embodiment.
Working examples of the present invention will now be given to
illustrate the effects of the invention.
EXAMPLE 1
A blended coal, A, formed solely of coking coal and a low grade
coal, B, indicated in Table 1 were blended in varying ratios
indicated in Table 2, treated with a fluidized bed 300 mm in
diameter to acquire respectively prescribed tool moisture contents,
placed in 18-liter tin cans, charged an electric furnace at
800.degree. C. and left to stand therein for four hours, then
heated up to 1000.degree. C. at a heating rate of 3.3.degree.
C./min., kept at this temperature for three hours, then discharged
from the electric furnace, quenched with sprayed water and tested
for coke strength in accordance with JIS K-2151-6. (This standard
will be invariably used in the tests to be indicated herein below).
The results are shown in Table 2.
TABLE 1 ______________________________________ Proximate analysis
(%) Particle Fix- size Vola- ed F.I. (Below Mois- tile car- (Log 3
mm) ture Ash matter bon CSN DDPM) (%)
______________________________________ Blend- ed 1.6 8.7 26.3 63.4
41/2 2.10 85 coal, A Low 2.7 8.8 34.1 54.4 1/2 No. 85 grade rota-
coal, B tion ______________________________________ (Note)
Proximate analysis was made in accordance with JIS M8812, CSN in
accordance with JIS M8801-5 and F1 in accordance with JIS M8801-7
respectively. (These standards will be invariably used in the tests
to be indicated herein below.)
TABLE 2 ______________________________________ To- Bulk tal density
mois- in tin Coke strength Run ture can DI.sub.15.sup.30
DI.sub.15.sup.150 No. Blending ratio (%) (kg/m.sup.3) (%) (%)
______________________________________ 1 Blended coal A 100% 8.0
750 93.8 83.0 2 " 6.0 800 94.1 83.9 3 " 4.0 850 94.6 86.1 4 " 2.0
870 94.8 86.5 5 " 0 870 94.8 86.6 6 Blended coal A 90% + 8.0 750
89.2 75.7 low grade coal B 10% 7 Blended coal A 90% + 5.0 810 90.8
76.8 low grade coal B 10% 8 Blended coal A 90% + 3.0 860 94.9 86.3
low grade coal B 10% 9 Blended coal A 90% + 0 870 95.4 86.4 low
grade coal B 10% 10 Blended coal A 80% + 8.0 750 85.2 68.7 low
grade coal B 20% 11 Blended coal A 80% + 5.0 810 87.8 74.9 low
grade coal B 20% 12 Blended coal A 80% + 3.0 860 93.3 82.5 low
grade coal B 20% 13 Blended coal A 80% + 0 870 93.8 82.9 low grade
coal B 20% 14 Blended coal A 70% + 0 870 91.4 78.2 low grade coal B
30% ______________________________________ (Note) Total moisture
content was determined in accordance with the method for simplified
measurement of total moisture content defined by JIS M8811-6; (This
method will be invariably used in the tests to be indicated herein
below.) Bulk density in the tin can was determined by placing a
10kg sample in an iron box 235 mm in width .times. 235 mm in length
.times. 355 mm in height, dropping the box from a height of 11 cm
onto an iron plate three times and finding the height of the sample
held in the box. (This method will be invariably used in the tests
to be indicated hereinbelow.)
It is seen from Table 2 that the effect of the preheating of the
blended coal A was particularly conspicuous in the test runs
involving total moisture contents of not more than 4% and the
blendability of the blended coal A for blending the low grade coal
B is limited to about 20%.
EXAMPLE 2
A blended coal, A, indicated in Table 1 above, was treated with the
aforementioned fluidized bed to acquire a varying prescribed total
moisture content ranging from 8% to 2%, and fed into the hopper 1
of a test apparatus illustrated in FIG. 1. Separately, masec type
briquettes (with a total moisture content fixed at 8% and 2%)
having a composition shown in Table 3 and measuring 35 mm.times.35
mm.times.25 mm were fed into the briquette hopper 2. By the
operation of the screw feeder 3 and the vibration feeder 4, the
blended coal, A and the briquettes, were drawn out of the hopper 1
and the briquette hopper 2 respectively at a prescribed proportion,
transferred through the medium of the scraper type conveyor 5 into
the full-scale model coke oven of steel plates improvised by
halving only lengthwise the carbonization chamber of a large coke
oven measuring 7.1 m in height, 16.5 m in length and 0.46 m in
width, and discharged through the sample outlet 7. The samples thus
obtained were tested for segregation of briquettes.
The results are shown in Table 4. The value given in the Table 4
represent averages of the five samples in heightwise of the
full-scale model coke oven.
TABLE 3 ______________________________________ Blending ratio (%)
______________________________________ Blended coal, A 40 Low grade
coal, B 60 Road tar (Additional) 7
______________________________________
TABLE 4
__________________________________________________________________________
Percentage of briquettes contained at varying position (%) Blending
Midway Percentage ratio of Oven Underside between of contained Max.
variation briquet- door of charging charging briquettes (R)
coefficient tes (%) side hole holes (max. - Min.) of briquettes
__________________________________________________________________________
Total moisture 8% 20 29.3 11.7 30.7 19.0 1.54 Blended coal, A 30
34.6 14.1 43.4 29.3 1.46 Total moisture, 8% 40 42.8 17.5 55.9 38.4
1.40 Briquettes 50 50.0 30.9 76.9 46.0 1.54 Total moisture 6% 20
30.1 11.9 30.2 18.3 1.51 Blended coal, A 30 35.3 13.0 42.0 29.0
1.40 Total moisture, 8% 40 43.1 19.8 58.0 38.2 1.45 Briquettes 50
51.1 28.5 74.0 45.5 1.48 Total moisture 4% 20 14.1 23.6 20.4 9.5
1.18 Blended coal, A 30 21.8 32.1 27.3 10.3 1.07 Total moisture, 8%
40 49.2 38.0 39.6 11.2 1.23 Briquettes 50 69.5 42.8 44.7 26.7 1.39
Total moisture 2% 20 14.2 22.2 20.8 8.0 1.11 Blended coal, A 30
27.4 31.2 29.8 3.8 1.04 Total moisture, 8% 40 46.9 36.8 37.5 10.1
1.17 Briquettes 50 65.9 41.9 45.6 24.0 1.32 Total moisture 2% 20
14.5 22.9 21.0 8.4 1.14 Blended coal, A 30 28.0 31.0 28.5 3.0 1.03
Total moisture, 2% 40 47.5 37.3 38.1 10.2 1.19 Briquettes 50 66.6
42.3 45.0 24.3 1.33 Total moisture 8% 20 31.2 10.3 32.0 21.7 1.60
Blended coal, A 30 35.0 13.9 44.5 30.6 1.48 Total moisture, 2% 40
41.6 18.2 59.3 41.1 1.48 Briquettes 50 48.7 29.7 78.1 48.4 1.56
__________________________________________________________________________
(Note) Max. variation coefficient of briquettes = Max. percentage
of contained briquettes/blending ratio.
It is seen from Table 4 that in the samples involving addition of
briquettes to the blended coal, A, having a total moisture content
of 8%, the percentages of contained briquettes were decreased to
the order of about 50% of the blending ratio of briquettes without
reference to the total moisture content of the briquettes and that
in the samples blending briquettes in the blending ratio of 40%,
portions having the maximum percentage of briquettes in the
neighborhood of 60% occurred locally within the coke oven,
suggesting the possibility of pushing troubles and other
difficulties in discharging from the coke oven.
In the case of the samples involving addition of briquettes to the
blended coals, A, having total moisture contents of 4% and 2%, the
variations in the percentages of contained briquettes are fairly
low in the range of 10 to 20% without reference to the total
moisture content of briquettes where the blending ratio of
briquettes are up to 40%, suggesting that even in the commercial
operation, the blending ratio of briquettes can be increased up to
40%.
The data indicate that the segregation caused in the coke oven by
the addition of briquettes depends more on the total moisture
content of the blended coal than on that of the briquettes. The
total moisture content of the briquettes was determined by the
method for determination of total moisture content (toluene
process) specified by JIS K-2425-9. (This method will be invariably
used in the tests to be indicated herein below.)
EXAMPLE 3
A blended coal, C, indicated in Table 5 and formed solely of coking
coal was treated with the same fluidized bed as used in Example 1
to acquire a total moisture content of 2%. The coal material for
briquetting, having the same composition as shown in Table 3, was
treated with a drier to acquire a stated total moisture content,
kneaded with 7% of added road tar at 50.degree. to 60.degree. C.
for 10 minutes and formed into masec type briquettes 35 mm.times.35
mm.times.25 mm with a roll press. The briquettes were mixed in a
blending ratio of 30% with the aforementioned blended coal, C. The
resultant blend was carbonized by the procedure of Example 1 and
the produced coke was tested for coke strength. The relation
between the total moisture content of the briquettes and the coke
strength is shown in FIG. 2.
TABLE 5 ______________________________________ Proximate analysis
(%) Particle Fix- size Vola- ed F.I. (Below Mois- tile car- (Log 3
mm) ture Ash matter bon CSN DDPM) (%)
______________________________________ Blend- ed 1.7 8.7 27.2 62.4
51/2 1.36 85% coal, C ______________________________________
Separately, the aforementioned material coal for briquetting in a
state retaining intact its total moisture content was kneaded with
7% of road tar added thereto at 50.degree. to 60.degree. C. for 10
minutes. The mixture was formed into masec type briquettes 35
mm.times.35 mm.times.25 mm with a roll press. The briquettes were
treated with a drier to acquire a total moisture content of 2% and
mixed in a blending ratio of 30% with the blended coal, C, having
an adjusted total moisture content of 2%. The resultant mixture was
carbonized under the same conditions as those of Example 1 and then
tested for coke strength, DI.sub.15.sup.30, which was found to be
93.5. This value is practically identical with the value 93.6 of
the coke strength, DI.sub.15.sup.30, found for the coke which is
produced by blending the briquettes of the type (having a total
moisture content of 2%) formed by first treating the material coal
for total moisture content adjustment and thereafter molding the
material coal with a roll press.
This fact shows that the effect of the blend of briquettes is the
same, no matter whether the briquettes are obtained by first
treating the coal material for to adjust its total moisture content
and thereafter molding the material coal with a roll press or are
obtained by first molding the material coal with a roll press and
thereafter treating the shaped blocks of coal material to adjust
their total moisture content. This means that the effect has
absolutely nothing to do with the procedure to be followed in the
preparation of the briquettes.
EXAMPLE 4
By following the procedure of Example 1, a blended coal, D, formed
solely of coking coal and a low grade coal, E, indicated in Table 6
were treated to have their total moisture contents adjusted to 8%
in some test runs and 2% in others and were mixed with each other
at varying ratios indicated in Table 7. The resultant blends were
mixed with the blended coal, D, low grade coal, E, and road tar at
the varying blended ratios also indicated in Table 7, kneaded at
50.degree. to 60.degree. for 10 minutes and thereafter mixed with
40% of masec type briquettes 35 mm.times.35 mm.times.25 mm formed
in advance with a roll press. The resultant mixtures were
carbonized by the procedure of Example 1 and tested for coke
strength.
The results are shown in Table 7.
TABLE 6 ______________________________________ Proximate analysis
(%) Particle Fix- size Vola- ed F.I. (Below Mois- tile car- (Log 3
mm) ture Ash matter bon CSN DDPM) (%)
______________________________________ Blend- ed 1.3 8.9 26.4 63.4
51/2 1.92 85 coal, D Low grade 2.6 10.0 32.9 54.5 1 1.0 85 coal, E
______________________________________
TABLE 7
__________________________________________________________________________
Blended coal Briquettes Blending ratio Blending ratio Total Low Low
Coke mois- Blended grade Total Blended grade Binder Total low
strength Run ture coal, D coal, moisture coal, D coal, Road tar
grade coal DI.sub.15.sup.150 No. (%) (%) E (%) (%) (%) E (%) (%)
content (%) (%)
__________________________________________________________________________
15 8.0 100 0 -- -- -- -- -- 83.4 16 8.0 100 0 8.0 60 40 7 16 84.1
17 8.0 100 0 8.0 40 60 7 24 83.4 18 8.0 100 0 8.0 20 80 7 32 82.6
19 2.0 100 0 -- -- -- -- 0 85.1 20 2.0 80 20 -- -- -- -- 20 83.4 21
2.0 60 40 -- -- -- -- 40 82.6 22 2.0 80 20 8.0 60 40 7 28 84.2 23
2.0 80 20 8.0 40 60 7 36 83.5 24 2.0 80 20 8.0 20 80 7 44 82.7 25
2.0 80 20 2.0 60 40 7 28 84.5 26 2.0 80 20 2.0 40 60 7 36 84.1 27
2.0 80 20 2.0 25 75 7 42 83.5 28 2.0 80 20 2.0 20 80 7 44 83.0
__________________________________________________________________________
It is seen from Table 7 that in Run No. 23, which involved combined
use of the preheated coal (blended coal, D) charging process and
the partial briquette charging process, the total low grade coal
content was 36%, a value about 12% more than the value 24% obtained
in Run No. 17, which represented sole application of the partial
briquette charging system. It is further seen that in Run No. 27,
which involved additional use of briquettes having an adjusted
total moisture content of 2%, the low grade coal could be blended
in a ratio of 42%.
These high low grade coal contents were ascribable respectively to
the synergistic effect of the combined use of the preheated coal
charging process and the partial briquette charging process and to
the synergistic effect of the additional use of dried
briquettes.
EXAMPLE 5
The same blended coal as used in Run No. 20 of Example 4 was mixed
with 40% of briquettes indicated in Table 9 and produced by the
procedure of Example 4. The resultant mixture was carbonized by the
procedure of Example 1 and the coke thus obtained was tested for
coke strength. The results are shown in Table 9.
The properties of the caking substance added in the briquettes are
shown in Table 8.
TABLE 8
__________________________________________________________________________
Softening Fixed Insolubles in solvent extraction (%) point carbon
n- Carbon Ultimate analysis (%) (.degree.C.) (%) hexane Benzene
disulfide Quinoline C H N S
__________________________________________________________________________
Caking 187 57.9 79.2 48.3 34.1 14.7 85.7 5.9 1.9 7.0 substance
__________________________________________________________________________
TABLE 9
__________________________________________________________________________
Briquettes Blended coal Blending ratio Blending ratio Road Coal Low
Low tar tar Total Blended grade Total Blended grade Caking (addi-
(addi- Total low Coke strength, Run moisture coal, D coal, moisture
coal, D coal, substance tional) tional) coal content
D.sub.15.sup.150 No. (%) (%) E (%) (%) (%) E (%) (%) (%) (%) (%)
(%)
__________________________________________________________________________
29 2.0 80 20 8.0 25 75 -- 7 -- 42 83.0 30 2.0 80 20 6.0 25 75 -- 7
-- 42 83.0 31 2.0 80 20 4.0 25 75 -- 7 -- 42 83.4 32 2.0 80 20 2.0
25 75 -- 7 -- 42 83.4 33 2.0 80 20 8.0 13.5 81 5.5 7 -- 44.4 83.0
34 2.0 80 20 6.0 13.5 81 5.5 7 -- 44.4 83.2 35 2.0 80 20 4.0 13.5
81 5.5 7 -- 44.4 83.9 36 2.0 80 20 2.0 13.5 81 5.5 7 -- 44.4 84.0
37 2.0 80 20 2.0 9.5 85 5.5 7 -- 46 83.4 38 2.0 80 20 2.0 4.5 90
5.5 7 -- 48 82.8 39 2.0 80 20 2.0 9.5 85 5.5 -- 7 46 83.4 40 2.0 80
20 2.0 4.5 90 5.5 -- 7 48 82.7
__________________________________________________________________________
It is seen from Table 9 that addition of the caking substance by a
blending ratio of 5.5% to briquettes permitted the blending ratio
of the low grade coal, E, into the briquettes to be increased by 6%
in the case of briquettes having a total moisture content of 8%,
and that the increase in the blending ratio was raised to 10% when
the total moisture content of briquettes was lowered to 2%.
This fact shows that the effect of the addition of the caking
substance into the briquettes is manifested more conspicuously when
the total moisture content of briquettes is lowered. Thus, the
reduction in the total moisture content brings about what may well
be called an unexpected effect.
EXAMPLE 6
Blended coals, F and G, of the respective compositions indicated
below were subjected to a varying pretreatment (I through IV)
described below, and placed in 18-liter tin cans, then the blended
coal was carbonized by the procedure of Example 1, and tested for
coke strength. The results of the test are shown in Table 10.
______________________________________ Blended coal, F: Strongly
coking coal from U.S.A. 25% Semi-strongly coking coal from
Australia 55% Domestic weakly coking coal 20% Blended coal, G:
Strongly coking coal from Australia 25% Semi-strongly coking coal
from U.S.A. 55% Domestic weakly coking coal 20%
______________________________________
Description of pretreatment:
I: The given blended coal was pulverized to an extent enough to
produce coal particles containing 80% of particles of sizes not
exceeding 3 mm and then was adjusted to acquire a total moisture
content of 8%.
II: The blended coal which had undergone Pretreatment I was
preheated at 200.degree. C. in a fluidized bed 350 mm in diameter
and then left to cool off on an iron plate.
III: Of the component coals making up a given blended coal, the
coking coal of Australian origin was pulverized. The resultant
particles were screened through a 6-mm sieve, and the coarse
particles retained on the sieve were again pulverized, to produce
particles containing 80% of particles of sizes not exceeding 3 mm.
The remaining two component coking coals were pulverized to produce
particles containing 80% of particles of sizes not exceeding 3 mm.
Then, these particles (course particles pulverized again and fine
particles passed the sieve of Australian origin, the other coking
coals) obtained as described above were mixed.
IV: The blended coal which had undergone Pretreatment III was
preheated at 200.degree. C. and then left to cool off on an iron
plate similarly to Pretreatment II.
TABLE 10 ______________________________________ Coke strength Pre-
Total Bulk density D.sub.15.sup.30 (%) Run treat- moisture in tin
can Blended Blended No. ment (%) (kg/m.sup.3) coal, F coal, G
______________________________________ 41 I 8.0 750 92.1 92.2 42 II
0 870 92.8 92.9 43 III 8.0 750 92.5 92.7 44 IV 0 870 93.6 93.5
______________________________________
TABLE 11 ______________________________________ Mesh size 4 mm Mesh
size 6 mm Kind of coal Screening Percentage CSN Percentage CSN
______________________________________ Strongly Retained 48.6 (%)
11/2 40.3 (%) 11/2 coking coal Passed 51.4 6 59.3 51/2
Semi-strongly Retained 49.1 11/2 37.9 11/2 coking coal Passed 50.9
6 62.1 5 ______________________________________ (Note) Table 11
shows the percentages at which the coal particles resulting from
the aforementioned pulverization of the coking coal of Australian
origin were partly retained on and partly passed through sieves 4
mm and 6 mm in mesh size when they were screened through the
sieves, and the respective CSN values.
EXAMPLE 7
The blended coal, F, of Example 6 was mixed at a varying blending
ratio with a low grade coal, H, shown in Table 12. The resultant
mixtures were subjected to the pretreatments of Example 6, with and
without modifications. Specifically, Pretreatments I and II were
performed in their unmodified form. Pretreatment III' comprised
pulverizing only the semi-strongly coking coal of Australian origin
of a given blended coal, screening the resulting particles through
a 6-mm sieve and pulverizing again the coarse particles retained on
the sieve to produce particles containing 80% of particles of sizes
not exceeding 3 mm, then mixing the pulverized course particles and
fine particles which passed the sieve of Australian origin with the
remaining coking coals and low grade coal H which had been
separately pulverized into particles containing 80% of particles of
sizes not exceeding 3 mm. And Pretreatment IV' comprised causing
the coal resulting from Pretreatment III' to be preheated at
200.degree. C. and then left to cool off on an iron plate similarly
to Pretreatment II. The blended coal obtained by each of the
pretreatments was carbonized and then tested for coke strength
similarly to Example 6. The results are shown in Table 13.
TABLE 12 ______________________________________ Proximate analysis
(%) Fix- Particle Vola- ed FI size Mois- tile car- (Log (below ture
Ash matter bon CSN DDPM) 3 mm)
______________________________________ Low 2.7 8.8 34.1 54.4 1/2 No
80% grade rota- coal tion
______________________________________
TABLE 13 ______________________________________ Blending ratio (%)
To- Coke Pre- Low tal Bulk density strength Run treat- Blended
grade mois- in tin can DI.sub.15.sup.30 No. ment coal, F coal, H
ture (kg/m.sup.3) (%) ______________________________________ 45 I
95 5 8.0 750 91.2 46 II 90 10 0 870 92.5 47 II 80 20 0 870 92.1 48
II 70 30 0 870 91.4 49 III' 95 5 8.0 750 92.1 50 III' 90 10 8.0 750
91.8 51 IV' 90 10 0 870 93.2 52 IV' 80 20 0 870 92.8 53 IV' 70 30 0
870 92.1 54 IV' 60 40 0 870 91.2
______________________________________
It is seen from Table 13 that in Run Nos. 51-54 involving
Pretreatment IV', namely, the steps of selectively pulverizing the
coking coal of Australian origin, mixing the resultant coal
particles with the other coking coals to form the blended coal, F,
combining the blended coal, F, with the low grade coal, H, and
thereafter treating the resultant blend for total moisture content
adjustment, blends were produced which each consisted of 70% of the
blended coal, F, and 30% of the low grade coal, H.
EXAMPLE 8
The material coal for briquetting prepared by blending the same low
grade coal, H, (Table 12) as used in Example 7 in a varying
blending ratio with the blended coal, G, of Example 6 and road tar
having a softening point of 25.degree. C. and added thereto as a
binder were kneaded at 50.degree. to 60.degree. C. for 10 minutes.
The resultant mixture was formed into masec type briquettes 35
mm.times.35 mm.times.25 mm with a roll press. The adjusted total
moisture content of the briquettes was 8% in some test runs and 2%
in others.
Then, the blended coal blended of 70% of the blended coal, G, of
Example 6 and 30% of the low grade coal, H, of Example 7 was
subjected to Pretreatment IV' and mixed with 40% of a varying type
of briquettes prepared as described above. The resultant mixture
was carbonized by the procedure of Example 6, and the coke was
tested for coke strength. The blending ratio of the material coals
for briquetting and the results of the test for coke strength are
shown in Table 14.
TABLE 14
__________________________________________________________________________
Total Blended coal (%) Briquettes (%) low Bulk Blending ratio
Blending ratio grade density Coke Low Low Binder coal in tin
strength Run Total Blended grade Total Blended grade (addi- content
can DI.sub.15.sup.30 No. moisture coal, G coal, H moisture coal, G
cla, H tional) (%) (kg/m.sup.3) (%)
__________________________________________________________________________
55 0 70 30 8.0 60 40 7 34 950 92.3 56 0 70 30 8.0 50 50 7 38 950
92.1 57 0 70 30 8.0 40 60 7 42 950 91.1 58 0 70 30 2.0 60 40 7 34
950 93.0 59 0 70 30 2.0 50 50 7 38 950 92.5 60 0 70 30 2.0 40 60 7
42 950 92.1 61 0 70 30 2.0 30 70 7 46 950 91.7
__________________________________________________________________________
It is seen from Table 14 that in the coke of the charging coal
consisting of 60% of the blended coal containing 30% of the low
grade coal, H, and 40% of the briquettes, the proportion of the low
grade coal to the whole amount of the charging coal was 38% when
the briquettes had a total moisture content of 8% (Run No. 56),
whereas the proportion could be increased to 42% when the
briquettes incorporated had a total moisture content of 2% (Run No.
60).
EXAMPLE 9
By the procedure of Example 8, briquettes were formed of what was
obtained by mixing the low grade coal, H, indicated in Table 12 in
a varying blending ratio with the blended coal, G, used in Example
6 and adding to the resultant mixture a binder (there was used coal
tar or road tar) and a caking substance as shown in Table 15. Then,
60% of the blended coal which was obtained by mixing the blended
coal, G, with 30% of the low grade coal, H, and subjecting the
resultant mixture to Pretreatment IV' was mixed with 40% of the
briquettes obtained as described above. The resultant blend was
carbonized by following the procedure of Example 6, and the coke
was tested for coke strength.
The composition of the briquettes and the results of the test for
coke strength are shown in Table 16.
TABLE 15 ______________________________________ Insolubles in
solvent extraction Softening Fixed (%) point carbon n- Carbon
Quino- (.degree.C.) (%) Hexane Benzene disulfide line
______________________________________ Caking 187 57.9 79.2 48.3
34.1 14.7 sub- stance ______________________________________
Ultimate analysis (%) C H N S
______________________________________ 85.7 5.9 1.2 7.0
______________________________________
TABLE 16
__________________________________________________________________________
Total low Blended coal (%) Briquettes (%) grade Bulk Blending ratio
Blending ratio coal density Coke Low Low Caking Binder con- in tin
strength Run Total Blended grade Total Blended grade sub- (Addi-
tent can DI.sub.15.sup.30 No. moisture coal, G coal, H moisture
coal, G coal, H stance tional) (%) (kg/m.sup.3) (%)
__________________________________________________________________________
62 0 70 30 8.0 39.5 55 5.5 Coal tar 40 950 92.2 7 63 0 70 30 8.0
34.5 60 5.5 Coal tar 42 950 91.4 7 64 0 70 30 8.0 39.5 55 5.5 Road
tar 40 950 92.1 7 65 0 70 30 2.0 29.5 65 5.5 Coal tar 44 950 92.7 7
66 0 70 30 2.0 19.5 75 5.5 Coal tar 48 950 92.1 7 67 0 70 30 2.0
9.5 85 5.5 Coal tar 52 950 91.6 7 68 0 70 30 2.0 19.5 75 5.5 Road
tar 48 950 92.1 7
__________________________________________________________________________
It is seen from Table 16 that the addition of the caking substance
in a blending ratio of 5.5% to the briquettes permitted the total
low grade coal content to be increased by 2% in the case of
briquettes having a total moisture content of 8% (Run Nos. 56-62)
and that the increase in the total low grade coal content rose to
6% in the case of briquettes having a total moisture content of 2%
(Run Nos. 60-66). This fact shows that the effect of the addition
of the caking substance into the briquettes is conspicuously
enhanced by a decrease in the total moisture content of the
briquettes.
EXAMPLE 10
Of the blended coal, G, shown in Example 6, the strongly coking
coal of Australian origin was pulverized. The resultant particles
were screened through a 6-mm sieve. The fine particles collecting
under the 6-mm sieve were mixed with the remaining semi-strongly
coking coal and weakly coking coal. The resultant mixture was
blended in a varying blending ratio with the low grade coal, H,
shown in Table 12 of Example 7. The blended coal thus obtained was
treated to be given an adjusted total moisture content of 2% and
carbonized by following the procedure of Example 6, and the coke
was tested for coke strength. The results are shown in Table
17.
TABLE 17
__________________________________________________________________________
Blending ratio (%) Particles of strongly Particles of strongly Bulk
coking coal of coking coal of Semi-strongly Weakly Low Density Coke
Run Australian orgin Australian orgin coking of coal coking grade
in tin can strength No. retained on the sieve passed through the
sieve U.S.A. origin coal coal, H (kg/m.sup.3) DI.sub.15.sup.30
__________________________________________________________________________
(%) 69 0 11.6 42.9 15.5 30 870 92.5 70 0 10.8 39.8 14.4 35 870 92.1
71 0 10.0 36.7 13.3 40 870 91.5
__________________________________________________________________________
It is seen from Table 17 that the blended coal formed without
blending the particles retained on the sieve of the strongly coking
coal of Australian origin abounded with inert particles and
permitted blending of as much as 35% of the low grade coal when the
blended coal was treated to be given an adjusted total moisture
content of 2%.
EXAMPLE 11
The particles retained on the sieve of the strongly coking coal of
Australian origin which were not blended in the blended coal in
Example 10 were further pulverized and used as the coal material
for briquetting. By following the procedure of Example 8,
briquettes were formed of what was obtained by mixing the
additionally pulverized particles with the caking substance
indicated in Table 15 and road tar or coal of Run No. 70 of Example
10, 40% of either varying the blending ratio of low grade coal or
the varying the total moisture content of the briquettes obtained
as described above were mixed. The resultant mixture was carbonized
by the procedure of Example 1 and the coke was tested for coke
strength. The blending ratios of material coals and the results of
the test for coke strength are shown in Table 18.
It is seen that the low grade coal content of the blended coal can
be increased to a great extent, as is plain from Example 9, by
using as the coal material for briquetting the particles retained
on the sieve of the strongly coking coal of Australian origin. It
is also clear from the present example that one half of the entire
charging coal is allowed to be substituted with low grade coal when
the total moisture content of briquettes is adjusted or the caking
substance is added into the briquettes.
TABLE 18
__________________________________________________________________________
Blended coal (%) Briquettes (%) Blending ratio Blending ratio
Particles Particles of strongly of strongly coking coal coal of of
Australian Australian origin Particles origin Particles passed of
strongly passed of strongly through Total coking coal through the
coking coal the sieve, low of sieve, semi of semi grade Australian
strongly Low Australian strongly Low coal Coke origin coking coal
grade origin coking coal grade Caking Binder con- strength Run
Total retained on and weakly coal, Total retained on and weakly
coal, sub- (addi- tent DI.sub.15.sup.30 5 No. moisture the sieve
coking coal H moisture the sieve coking coal H stance tional) (%)
(%)
__________________________________________________________________________
72 0 0 65 35 8 15.2 39.8 45 0 Road 39 92.1 tar 7 73 0 0 65 35 8
13.7 25.8 55 5.5 Coal 43 92.2 tar 7 74 0 0 65 35 2 14.2 30.8 55 0
Coal 43 92.1 tar 7 75 0 0 65 35 2 12.2 12.3 70 5.5 Coal 49 92.1 tar
7 76 0 0 65 35 2 12.2 12.3 70 5.5 Road 49 92.2 tar 7
__________________________________________________________________________
* * * * *